Construction element for building that accumulates latent heat

ABSTRACT

The invention relates to a construction element that comprises at least one first transparent pane and a parallel second pane that is at least partly transparent and contains a material that accumulates latent heat. The material that accumulates latent heat is dyed or pigmented so that it absorbs light in the infrared range of the solar spectrum. The construction element claimed by the invention is highly efficient in absorbing light directly in the material that accumulates latent heat.

[0001] CH-A-688 describes a construction element that accumulates latentheat as described in the introduction to claim 1. One of the walls of aspace is enclosed from the exterior by a wall which has on the outside atransparent thermal insulation and on the inside a space formed by twopanes. This space is occupied by a substance that accumulates latentheat, such as calcium chloride hexahydrate, for example.

[0002] The object of this invention is to develop a construction elementof the type described above so that it is more efficient in terms oflight absorption. This object is accomplished by the features disclosedin the characterizing portion of claim 1 and by the features disclosedin the dependent claims.

[0003] The invention is explained in greater detail below with referenceto the exemplary embodiments that are illustrated in the accompanyingdrawings, and in which:

[0004] FIGS. 1-6 show cross sections through different embodiments ofthe invention.

[0005] The construction element illustrated in FIG. 1 consists oftransparent panes 10, 11 that can be fabricated from glass or plastic.They form a space between them. This space is sealed and filled with amaterial 12 that accumulates latent heat. The heat of melting of thematerial 12 that accumulates latent heat is utilized to store thermalenergy. Preference is given to the use of a material that melts at roomtemperature, such as calcium chloride hexahydrate or paraffin. In thismanner, it becomes possible during the melting process in the range ofroom temperature to store several times more thermal energy in thematerial that accumulates latent heat than in conventional constructionmaterials such as concrete or brick. These materials are poured into thespace at temperatures that are above the melting point or areco-extruded with the panes 10, 11. It is also possible to introduce thematerial that accumulates latent heat between the panes 10, 11 in solidform. The air in the minimal voids is then advantageously evacuated, sothat it does not adversely affect the thermal conduction of theconstruction element. When paraffin is used as the material thataccumulates latent heat, it is also possible to also make the paraffinretain its shape even during the solid/liquid phase transition by usingsupporting materials. The paraffin is distributed in the supportingmaterial completely uniformly, and no liquid paraffin escapes even athigh operating temperatures. An additional method of introducing theparaffin between the panes 10, 11 so that it retains its shape is toenclose the paraffin in sealed hollow bodies 25, so that these hollowbodies filled with paraffin can be stacked in a dry process between thepanes 10, 11. These hollow bodies are advantageously fabricated fromplastic. Some or all of the static pressure that is produced by thestacked hollow bodies 25 can thereby be used to make the hollow bodies25 adhere to one another and to the panes 10 and 11. The result is astatic composite structure that also increases the stability of thepanes 10, 11.

[0006] The material 12 that accumulates the latent heat is dyed orpigmented so that it absorbs light in the infrared range of the solarspectrum. It is preferably a dark color, so that the sunlight isabsorbed directly in the material 12 that accumulates latent heat. Theabsorbed energy is stored in the form of thermal energy in the materialthat accumulates latent heat and is discharged slowly and continuouslyin the form of thermal radiation into the interior of the room. Thiscolor must be dark enough that as much incident solar radiation aspossible is absorbed by the material 12 that accumulates latent heatwithout overheating the interior of the room with the transmitted solarradiation. The absorptivity of the coloring must be determined as afunction of the location and the type of construction of the building.For example, on a building that uses lightweight construction, where theconstruction element forms an exterior wall directly, more light isabsorbed in the material that accumulates latent heat than in a buildingwith a more solid construction, in which the construction is a facadeelement that covers a wall. Other factors that must also be taken intoconsideration include the conventional window area of the facades facingthe sun and the expected solar radiation at the location of thebuilding. During the absorption of sunlight in the material 12 thataccumulates latent heat, the characteristics of the material are alsoutilized to advantage. The latent heat storage material paraffintransmits significantly more light in its liquid state than in the solidstate. It also has poor thermal conductivity. That means that when thelayer of material that accumulates latent heat is exposed to solarradiation, it melts slowly from the outside to the inside, and thus thelight transmission also increases from the outside to the inside.Consequently, the solar radiation ideally reaches the entire layer ofmaterial that accumulates latent heat and is stored where it isabsorbed. So that the solar radiation can more effectively melt theparaffin 12, the hollow bodies 25 are provided with depressions 26 oropenings to create apertures for the entry of light. The solar radiationthat comes through the apertures travels deeper into the layer ofmaterial 12 that accumulates latent heat.

[0007] A further possibility of increasing the degree of absorption ofthe construction element is to color the transparent panes 10, 11 or thehollow bodies 25 a dark color, to paint them a dark color or to providethem with a dark coating. These colorings or coatings of the panes 10,11 and of the hollow bodies 25 can also be used for decorative purposes.Facing the outside of the building, the panes 10, 11 are lined on theoutside with a transparent thermal insulation 13 which is enclosed byone or more additional transparent panes 14. The thermal insulation 13can be realized, for example, as described in WO 98/51973, which isincorporated into this application by reference. The pane 14 isadvantageously made of low-iron flint glass with a high lighttransmittance to optimize the transmission of light. For the transparentinsulating layer 13, transparent plastic honeycomb or other transparenthollow chamber constructions can also be used. These transparent thermalinsulators 13 have the characteristic that the air that is enclosed inthe hollow chambers acts as an insulator, while the hollow chambers areso small that the convection of the air is eliminated.

[0008] The transparent thermal insulation can also be used to fill thespace between the center pane 11 and the outer pane(s) 14 with an inertgas, e.g. argon, krypton or xenon, that is an effective thermalinsulator. An additional possibility is to evacuate the air in thisspace. A vacuum is an ideal insulator. The middle panes 11 and 14 canhave a thermal insulating coating 15 (FIG. 2) on the outside or insidethat is also called a Low-E coating. The outer flint glass pane 14 andthe gas or vacuum layer behind it have high light transmittance. Themiddle glass pane 11 that is coated with thermal insulation naturallyhas a reduced degree of total energy transmission. The incidentabsorption energy is not lost energy, but is diverted inward into thematerial that accumulates the latent heat, because the outsideinsulating layer and the thermal protection coating 15 prevent anythermal loss to the exterior.

[0009] So that the thermal element does not overheat in summer, there isa shading on the outside of the layer of material that accumulateslatent heat. In the exemplary embodiment illustrated in FIG. 2, theshading device 16 is located in the outer insulating space behind theexternal glass pane 14. This arrangement guarantees that theconstruction element with protection against overheating is manufacturedin the form of a stable, efficient and reliable unit that does notrequire the use of additional shading constructions.

[0010] An additional possible way of regulating the radiation resultsfrom the fact that the outer pane 24 has prismatic elevations 17. Bydeflecting the light, the sunlight that is incident at a higher angle inthe summer is deflected outward while the sunlight that is incident at alower angle can pass through the pane 24 unhindered. The prisms 17 canbe located both on the front side and on the reverse side of the pane14. The principle of deflected light can also be used to productholograms, although such applications are still relatively complex andexpensive. The construction element can also be used as a heatingelement. In a solar-heated house, additional heating sources are alsorequired to provide the make-up heat that is required in bad weather.The pane 10 can be realized in the form of an electrical flat resistanceradiator 18 facing the material 12 that accumulates the latent heat. Forthis purpose, conductive metal coatings are applied to the glass pane10. An additional possibility is to integrate pipes 19 that carry waterinto the latent heat storage system, and as in a flat radiator, thewater gives up its heat to the material that accumulates the latent heatas necessary. The material 12 that accumulates the latent heat makes itpossible to feed cheaper night-rate electricity into the material thataccumulates the latent heat, which can be then used later during the dayin the form of heat.

[0011] An additional possible protection against summertime overheatingis a metal oxide coating on the outside of the panes 14 or 11. Thegreater the incident angle with reference to a line perpendicular to thepanes 14, 11, the greater the reflection on the outer surface of thepanes 14, 11. In other words, summer sunlight that is incident at asteeper angle is reflected to a greater extent than winter sunlight thatis incident at a lower angle. This configuration is also an economicalsolution.

[0012] To optimize the economy of the construction element, it can beextruded in the form of a one-piece plastic element. When the material12 that accumulates the latent heat is loose, macroscopic cavities 20are required to hold the material 12 that accumulates the latent heat,which material does not retain its shape in its liquid state. It isadvantageous if the amount of transparent plastic used to form thecavities 20 in the panes 10, 11 is minimized and the cavities aresimultaneously realized so that they have a maximum capacity. Thisconfiguration can result in lattice-like structures as illustrated inFIG. 5. To optimize the efficiency of the web plates, especially inwinter, the webs 21, 22 can form an acute angle with the pane 14.

1. Construction element to accumulate latent heat for buildings,comprising at least one first transparent pane (14) and a second pane(10, 11; 23) parallel to said first pane, which second pane contains amaterial (12) that accumulates latent heat, characterized by the factthat the material (12) that accumulates latent heat is dyed or pigmentedso that is absorbs light, at least in the infrared range of the solarspectrum.
 2. Construction element as claimed in claim 1, whereby thefirst pane (14) is separated from the second pane (10, 11; 23) bytransparent thermal insulation (13).
 3. Construction element as claimedin claim 1, whereby a shading device (16) is located in the spacebetween the first pane (14) and the second pane (10, 11). 4.Construction element as claimed in one of the claims 1 to 3, whereby thematerial (12) that accumulates latent heat is co-extruded with thesecond pane (23).
 5. Construction element as claimed in one of theclaims 1 to 4, whereby the material (12) that accumulates latent heatcontains a paraffin or salt hydrate that melts at room temperature. 6.Construction element as claimed in claim 5, whereby the material thataccumulates latent heat is bonded in a supporting material. 7.Construction element as claimed in one of the claims 1 to 5, whereby thematerial (12) that accumulates latent heat is contained in hollow bodies(25).
 8. Construction element as claimed in claim 7, whereby the hollowbodies (25) have depressions (26) or apertures on the outside and/orinside.
 9. Construction element as claimed in one of the claims 1 to 8,whereby one of the panes (10, 11, 14) is coated with a Low-E coating(15).
 10. Construction element as claimed in one of the claims 1 to 9,whereby the material (12) that accumulates latent heat can be heated byheating elements (18, 19).
 11. Construction element as claimed in one ofthe claims 1 to 10, whereby the pane or one of the first panes (14, 24)has prismatic elevations (17) on one side, so that when the sun is at ahigh angle, the sunlight is deflected outward, and when the sun is at alow angle, the sunlight passes through the first pane (14) unhindered.12. Construction element as claimed in one of the claims 1 to 11,whereby at least a portion (10) of the second pane (10, 11) or thehollow bodies (25) are colored or coated in a dark color.